Numerical Simulation On Characteristics Of Flow Behavior In Inverse Liquid-Solid Fluidized Bed And Spouted Bed Based On Euler-Lagrangian Method

In the liquid-solid fluidization,surface-treated hydrophobic aerogel granules are fluidized by a downward flow of oil-contaminated water under the action of gravity and drag to achieve the purpose of oil droplet capture.Therefore,the technology of fluidization is gradually applied to the field of oil wastewater treatment.Because of the lack of practical application and the complexity of liquid-solid two-phase flow,this paper chooses the method of numerical simulation to study the hydrodynamics characteristics of a binary system of particles of liquid-solid two-phase flow in the inverse liquid-solid fluidized bed and the inverse liquid-solid spouted fluidized bed to provide some theoretical basis for practical production in industry.Based on the Eulerian-Lagrangian theory framework,the two-dimensional numerical simulation of the two-component particles in the inverse liquid-solid fluidized bed established by Quevedo et al and the quasi-two-dimensional numerical simulation of the flow characteristics of the two-component particles in the inverse liquid-solid spouted bed are carried out by using the CFD-DEM method.Eulerian model and Lagrangian particle tracking method are used to model the liquid and solid phases respectively and the Gidaspow drag force model is used to solve the drag force between the liquid and solid phases and the standard k-? model is used to describe the effects of liquid turbulence.The characteristics of flow behavior of liquid-solid two-phase flow in the inverse liquid-solid fluidized bed and spouted bed are found to depend mainly on the operation parameters(the inlet oil concentration in water and inlet liquid velocity)and the physical parameters(the aerogel-oil restitution coefficient,the viscosity of liquid and the size of aerogel particles).The results of simulation show that in an inverse liquid-solid fluidized bed,increasing t the aerogel-oil restitution coefficient can increase the kinetic energy of particles and increase the pulsation of particles,which is conducive to improving the fluidized state of particles.With the increasing of liquid viscosity and inlet liquid velocity,the expansion height of the bed can be up to 3.1 times,and even the particles of oil flow out of the fluidized bed under the carrying effect of the liquid phase.When the inlet oil concentration increases from390mg/L to 780mg/L,the phenomenon of particle stratification begins to appear in the fluidized bed,which makes the mixing degree of two-component particles worse and reduces the efficiency of wastewater treatment in the fluidized bed.Compared with the inverse liquid-solid fluidized bed,The particle concentration is symmetrically distributed and the diameter of jet is narrow in the upper part and wide in the lower part in the inverse liquid-solid spouted bed.As the aerogel-oil restitution coefficient increases,the agglomeration of binary particles on the right wall of the bed is improved considerably.As the inlet velocity of liquid decreases and the size of aerogel particles increases,the maldistribution of liquid-solid two-phase flow in the spouted bed can be improved obviously.When the inlet oil concentration is increased,it is found that there is no particle stratification in the spouted bed,so that the number of oil particles that can be completely fluidized can be increased by more than 2 times,and the sewage treatment capacity of the spouted bed is enhanced.